1. Technical Field
The present invention relates to a piezoelectric device in which a piezoelectric resonator element is housed in a package, and a method for manufacturing a piezoelectric device.
2. Related Art
Piezoelectric devices, including a piezoelectric resonator and a piezoelectric oscillator housing a piezoelectric resonator element in a package, have been widely used for small information equipment, such as hard disc drives (HDD), mobile computers and integrated circuit (IC) cards, for mobile communications equipment, such as cellular phones, car phones and paging systems, and for measuring instruments such as gyro sensors.
Namely, such piezoelectric devices are known that a piezoelectric resonator element is housed in a package and then the package is sealed by a lid such as a glass plate.
FIG. 13 shows such piezoelectric device 1 (see FIG. 1 of JP-A-2006-196932).
Referring to the figure, the piezoelectric device 1 includes a package (base) 2 made of ceramic and houses a piezoelectric resonator element 3 in the package 2 in a manner that a base portion 4 of the piezoelectric resonator element 3 is bonded to an electrode part in the package with a conductive adhesive 5.
Between a bonding surface being an upper end of the package 2 and a lid 6 made of glass, a low-melting glass 7 is disposed. Then a brazing material that is the low-melting glass is heated to be melted, bonding the lid 6 to the package 2 air-tightly.
Here, in the structure of FIG. 13, the lid 6 is bonded with the low-melting glass. The low-melting glass needs relatively large bonding surface, namely an area of a bonding allowance for the package 2 and the lid 6.
However, the large bonding allowance is hard to be maintained in the package 2 that is miniaturized. The bonding allowance is 0.4 mm or less, for example 0.2 mm, in width, at present. Therefore, if the low-melting glass is used as the brazing material, the bonding strength decreases, causing insufficient air-tightness of the package.
Further, in a case where the lid is made of material other than glass as well, if frequency of the piezoelectric resonator element 3 housed in the package can be adjusted after the package is sealed by the lid, a piezoelectric device miniaturized and having excellent frequency accuracy can be obtained preferably.